Retractable and removable king pins are needed on vehicle trailers to accomodate different tractors and still meet the length, axial load, swing clearance, and other legal as well as operational limitations. King pins are also needed to facilitate transporting the vehicle trailer on flat bed railroad cars. The trailer hitch location on a flat bed railroad car has been set by the optimum dry cargo van geometry which limits the length of a refrigerated vehicle trailer. A typical flat bed railroad car has a length of 89 feet, 4 inches and will accomodate two trailer vehicles. If the trailer vehicles are refrigerated, their maximum length is only 41 feet, 4 inches. The present invention will enable such refrigerated trailers to have a length of 42 feet, 6 inches.
Existing retractable king pin designs require the king pin to have some play in its mounting. Under cyclic loading and vibratory conditions, this results in rapid wear of the mating surfaces and there is no take-up provision for such wear. The geometry of these designs is unsuitable to transmit the extremely high loads encountered when the vehicle trailers are mounted on a flat bed railroad car. Any prior king pin arrangements known to me which are sufficiently rigid so as to have the necessary strength under such conditions, have other disadvantages particularly in connection with the time and effort required to transfer from one king pin position to another.
For a pivotably mounted king pin having a cooperative latch, see U.S. Pat. Nos. 2,981,555 and 3,791,674. It is known to provide a pair of king pins connected together by way of a common shaft as taught by U.S. Pat. No. 2,831,704. It is known to provide a single king pin which is adjustable forward and aft as taught by U.S. Pat. Nos. 2,976,051 and 3,770,296.